Reference Guide

rate of change of data is faster than the bandwidth of the replica link between the sites for large periods of time. This is critical

and must be taken into consideration when designing the solution.

NOTE: Both replication scenarios affect application performance because each data block has to be written multiple times,

assuming that all volumes are configured for replication.

NOTE: Stretched cluster with Storage Replica is not a substitute for a backup solution. Stretched cluster is a disaster

recovery solution that keeps a business running in the event of a site failure. Customers should still rely on application and

infrastructure backup solutions to recover lost data due to user error or application/data corruption.

Validated network topology

Basic configuration

This section describes the host network configuration and network cards that are required to configure a basic stretched

cluster. The purpose of this topology is to keep the host and inter-site configuration simple with little or no change to a standard

standalone cluster networking architecture.

Here we use two 25 GbE NICs for each host on both sites. One NIC is dedicated to intra-site storage traffic, similar to a

standalone Storage Spaces Direct environment. The second NIC is used for management, compute, and Storage Replica traffic.

To ensure management traffic is not bottlenecked due to high traffic on the Replica network, we request the customer network

team to throttle traffic between the two sites using firewall or router QoS rules. It is recommended that the network is throttled

to 50 percent of the capacity of the total number of network cards supporting the management NIC team.

The management network is the only interface between the two sites. Because only one network pipe is available between the

hosts on Site A and Site B, you will see the following warning in the cluster validation. This is an expected behavior.

Node SiteANode1.Test.lab is reachable from Node SiteBNode1.Test.lab by only one pair of

network interfaces. It is possible that this network path is a single point of failure

for communication within the cluster. Please verify that this single path is highly

available, or consider adding additional networks to the cluster.

Table 4. Sample IP address schema

Site A Site B Type of traffic

Management/Replica Traffic 192.168.100.0/24 192.168.200.0/24 L2/L3

Intra-site Storage (RDMA) - 1 192.168.101.0/24 192.168.201.0/24 L2

Intra-site Storage (RDMA) - 2 192.168.102.0/24 192.168.202.0/24 L2

VMNetwork/Compute

Network

As per customer environment As per customer environment L2/L3

The following figure shows the network topology of a basic stretched cluster:

Solution deployment